TOXICITY OF AN ORGANOPHOSPHATE PESTICIDE TO THREE HETEROTROPH SPECIES IN COSTA RICAN LOWLAND WET FOREST STREAMS
Ethoprophos, an organophosphate insecticide, is widely used on fruit plantations in Central America and has the potential to be transported beyond plantations (via air or waterways) to affect aquatic ecosystems in protected areas. Our goal was to identify the threshold concentrations at which ethoprophos impacts the behavior and survival of three common species of tropical lowland wet forest stream heterotrophs (the mayfly Traverella holzenthali, caddisfly Phylloicus sp., and guppy Priapichthys annectens) at La Selva Biological Station, Costa Rica. We predicted that mayflies and caddisflies, taxa considered sensitive to pollution, would have lower toxicity thresholds than P. annectens. Our preliminary data suggest that the lowest observed effect concentration (LOEC) may be as low as 100 ?g/L for Priapichthys annectens, with an LD50 of approximately 1500 ?g/L. The LD50 value for Phylloicus is approximated to be below 10 ?g/L with LOEC as low as 2?g/L. The LD50 of Traverella appears to be around 50 ?g/L, and LOEC may be lower than 1 ?g/L. These results support our prediction and underscore the need for further study of the ecological effects of pesticides. Our future work will include more accurate quantification of threshold concentrations.
Rebecca Prest (Primary Presenter/Author), Missouri Western State University, email@example.com;
Carissa Ganong (Co-Presenter/Co-Author), Missouri Western State University, firstname.lastname@example.org;